It's called 'straddling'. This way, the space between your legs (which is about the same width as your shoulders) serves as a convenient location to store said

It's called 'straddling'. This way, the space between your legs (which is about the same width as your shoulders) serves as a convenient location to store said bag, while also allowing you to stand over it and thereby protect it from trips/kicks and reduce your overall surface footprint.